1. Field of the Invention
This invention relates to a radiation image read-out apparatus, wherein a stimulable phosphor sheet, on which a radiation image has been stored, is exposed to stimulating rays, and an image signal representing the radiation image is detected from the stimulable phosphor sheet.
2. Description of the Related Art
It has been proposed to use stimulable phosphors in radiation image recording and reproducing systems. Specifically, a radiation image of an object, such as a human body, is recorded on a sheet provided with a layer of the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet). The stimulable phosphor sheet, on which the radiation image has been stored, is then exposed to stimulating rays, such as a laser beam, which cause the stimulable phosphor sheet to emit light in proportion to the amount of energy stored thereon during its exposure to the radiation. The light emitted by the stimulable phosphor sheet, upon stimulation thereof, is photoelectrically detected with photoelectric read-out means, such as a photomultiplier, and converted into an electric image signal. The image signal is then processed and used for the reproduction of the radiation image of the object as a visible image on a recording material.
In the radiation image recording and reproducing systems described above, the light is emitted in a scattering state from the stimulable phosphor sheet. Therefore, alight guide member and a light guiding mirror are located in the vicinity of the position that is exposed to the stimulating rays. The light emitted in the scattering state from the stimulable phosphor sheet is reflected by the light guiding mirror toward the light guide member. In this manner, the efficiency, with which the emitted light is collected, is enhanced.
The light guiding mirror described above is supported by support means, which is formed from a metal. The support means is secured by screws, or the like, to a frame within a radiation image read-out apparatus. Therefore, the support means is in a grounded state (i.e., in the state in which the support means is electrically connected with a ground). In cases where the radiation image is read out from the stimulable phosphor sheet having been charged electrostatically, lines of electric force concentrate upon the support means, and dust clinging to the stimulable phosphor sheet clings to the light guiding mirror by electrostatic adsorption. If the dust clings to the light guiding mirror in this manner, the stimulating rays will be eclipsed by the dust. In such cases, since the stimulable phosphor sheet is also scanned with the stimulating rays in a sub-scanning direction, streak-like nonuniformity in image density occurs in the sub-scanning direction. Also, the light guiding mirror is formed with, for example, a technique, wherein a dichroic coating layer is formed on a glass substrate. Therefore, the light guiding mirror is adhered to the support means with an adhesive agent. In such cases, if the adhesive agent protrudes from the area of adhesion of the light guiding mirror and dust clings to the protruding adhesive agent, it will become difficult to remove the dust.